Current shunts have been used to measure high currents in electrical systems, such as solar power electrical systems and wind power electrical systems. A typical current shunt includes the electrical equivalent of a low value resistor placed in series with an electrical system so that all of the current to be measured flows through the current shunt. The shunt resistance is typically as low as possible so that use of the current shunt does not affect or change circuit characteristics. The voltage drop across the current shunt is measured to determine the current flowing through the shunt.
Many current shunts are rectangular in shape with separate current connections and voltage sensing connections. A sensing element that is narrow in width relative to the current shunt is often coupled between the voltage sensing connections for measuring the voltage across the current shunt. A typical sensing element may include a narrow wire/conductor or circuit card trace that is coupled to a voltage measurement device for measuring the voltage across the current shunt.
For example, FIG. 1 illustrates an exemplary known current shunt 100 for high current applications. The current shunt 100 includes high current terminals 110 that can be coupled in series with a load through terminal connections 112. Current shunt 100 includes a shunt portion 120 having a resistance that is known to a high degree of accuracy. Current shunt 100 further includes a pair of separate sensing terminals 125 to measure the voltage across the current shunt 100. A sensing element 130 that comprises a narrow trace disposed on a circuit card 135 is coupled between sensing terminals 125. Sensing element 130 is coupled to a plug connection 140 for coupling to a suitable voltage measurement device. As shown in FIG. 1, sensing element 130 has a width that is narrow relative to the current shunt 100.
At low frequencies, the sensing voltage measured by a narrow sensing element, such as a narrow wire/conductor or narrow trace on a circuit card, is dependent on the current flowing through the current shunt. However, at higher frequencies, eddy currents caused by the skin effect can result in a non-uniform distribution of the current flow across the current shunt. More particularly, as the frequency of the current flowing through the current shunt increases, a greater portion of the current flows through the edges of the current shunt than at the middle or center of the current shunt. This causes the voltage drop across the edges of the current shunt to be different than the voltage drop across the center of the current shunt.
A narrow sensing element, such as a wire/conductor or narrow trace, typically only accounts for a voltage drop across a portion of the current shunt. For instance, the narrow sensing element 130 depicted in FIG. 1 will measure a voltage drop primarily attributable to current flowing through the middle of the current shunt 100. Because the current distribution across the current shunt 100 will vary at higher frequencies, measurements made by a narrow sensing element, such as narrow sensing element 130, may be inaccurate.
Thus, a need exists for an apparatus and method for improved current shunt sensing that results in more accurate sensing across a wider range of frequencies.